Germanwings co-pilot Andreas Lubitz may have spiked captain's drink with diuretic to force him from cabin

Prosecutors are searching Lubitz's computers for evidence

Lubitz may have 'spiked' the captains drink to make him go to the bathroom (Getty Images)

Investigators probing last month’s Germanwings crash are trying to determine whether the Andreas Lubitz placed a chemical in the captain’s drink to force him to go to the toilet.

The 27-year-old co-pilot crashed the Airbus 320 into an Alpine ravine in France, killing himself and the other 149 passengers and crew on board.

A black box recorder found in the flight revealed that Lubitz locked the cockpit door when the captain left for a toilet break. He then used controls to override the entry code, and took the chance to crash the plane as the captain desperately tried to break back in.

German prosecutors investigating Lubitz's computer are now attempting to confirm whether Lubtiz secretly added a diuretic – which gives a person the urge to urinate - to Captain Patrick Sodenheimer's coffee to make him leave the flight deck, according to reports in Germany seen by Mail Online.

Investigators have already uncovered how Lubitz searched for suicide methods and information on cockpit doors before the crash.

In the days running up to the tragedy, Lubitz, who was known to have suffered with depression, logged on to his computer under the name “Skydevil” and searched for information on cockpit security.

Between 16 to 23 March – the day before the disaster – Lubtiz repeatedly searched terms including “bipolarity”, “manic depression”, “migraines”, “impaired vision” and “acoustic trauma”, investigators with access to a tablet computer found in his apartment told Bild am Sonntag newspaper.